1. Field of the Invention
The present invention relates generally to an electrophotographic system such as a color laser beam printer and a color copier. More particularly, the present invention relates to an apparatus and a method for optimizing an image transfer environment in an electrophotographic system from sensing of humidity contained in a printing medium.
2. Description of the Related Art
Generally, in an electrophotographic system used in a copier, laser printer, facsimile machine, etc., a charging roller is rotated and evenly charges a photosensitive body on the outer peripheral surface of a photosensitive drum with a high pressure.
Moreover, the photosensitive body which is charged on the outer peripheral surface of the photosensitive drum forms an electrostatic latent image by a light emitted from an optical source of an exposing device such as a laser diode which changes an image digital signal to a laser beam.
At this time, the electrostatic latent image formed on the photosensitive drum is developed by a developing substance, such as toner powder when passing through a developer, and then it is changed into a visible toner image. The visible toner image is transferred onto a printable medium, that is printing paper, and then it is fixed on the printing paper by fusing the transferred visible toner image.
Meanwhile, such an electrophotographic system can print a color image if it is provided with plural color toners. Like the widely known multicolors image forming apparatus capable of displaying yellow, magenta, cyan, and black colors, a multicolor electrophotographic system accomplishes display of multicolors by means of four color toners, that is, yellow, magenta, cyan, and black.
Recently, an electrophotographic system has been most desirable in printing an image with high resolution, but its price is very high. However, since the system has advantages of high printing speed, fine image quality, superior durability etc., its use has been escalated in all applications.
In relation to the above electrophotographic system, many exemplars of contemporary practice are disclosed. Among the exemplars of the contemporary practice on this matter, Ehara et al.(U.S. Pat. No. 5,689,768, ELECTROPHOTOGRAPHING APPARATUS FOR COLLECTING TONER FROM A PHOTOSENSITIVE MEMBER AND CONVEYING IT TO DEVELOPING MEANS, Nov. 18, 1997) discusses an electrophotographing apparatus with a reusable toner system. Akinaga et al.(U.S. Pat. No. 5,740,504, ELECTROPHOGOGRAPHING METHOD USING CARONA CHARGINGDEVICEHAVINGAREAS WITH AND WITHOUT A GRID, Apr. 14,1998) discusses a charging effected using both areas relative to the grid. Tanaka et al.(U.S. Pat. No. 5,592,262, IMAGE FORMING APPARATUS WITH INK JET AND ELECTROPHOTOGRAPHIC RECORDING UNITS, Jan. 7, 1997) discusses a plurality of different image forming units for recording with different methods. Sakaizawa et al.(U.S. Pat. No. 5,734,390, IMAGE FORMING APPARATUS, Mar. 31, 1998) discusses a hybrid type image forming apparatus capable of forming a high quality image by using two image forming units having different resolution from each other. Sato et al.(U.S. Pat. No. 5,479,242, FAN SYSTEM FOR ELECTROPHOTOGRAPHIC APPARATUS, Dec. 26, 1995) discusses a fan system for an electrophotographic apparatus which is provided to simultaneously induce air flow over or through at least two components of the electrophotographic apparatus. Hattori(U.S. Pat. No. 5,665,510, TONER FOR ELECTROPHOTOGRAPHAND PROCESS FOR THE PRODUCTION THEREOF, Sep. 9,1997) discusses a toner for electrophotography which contains a binder resin having a low softening point so that the toner can be fixed at a low temperature, and which is free from blocking. Furukawa(U.S. Pat. No. 5,625,437, IMAGE FORMING APPARATUS, Apr. 29, 1997) discusses an image forming apparatus in which downsizing of the entire apparatus can be attained. Shigematsu et al.(U.S. Pat. No. 5,595,846, PHTHALOCYANINE MIXED CRYSTAL, PRODUCTION METHOD THEREOF, AND ELECTROPHOTOGRAPHIC PHOTORECEPTOR, Jan. 21, 1997) discusses an electrophotographic photoreceptor composed of an electrically conductive substrate having formed thereon a photosensitive layer containing a phthalocyanine mixed crystal comprising titanyl phthalocyanine and hydrogen phthalocyanine. Chern et al. (U.S. Pat. No. 5,007,690, HOLOGRAPHIC DATA STORAGE AND RETRIEVAL SYSTEM, Apr. 16, 1991) discusses a plurality of reflective diffusing holographic memory elements. Tanaka(U.S. Pat. No. 5,527,653, ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MEMBER, PROCESS CARTRIDGE AND ELECTROPHOTOGRAPHIC APPARATUS WHICH EMPLOY THE SAME, Jun. 18, 1996) discusses an electrophotographic photosensitive member including a conductive substrate and a photosensitive layer thereon. Fukushima et al.(U.S. Pat. No. 5,512,983, ELECTROPHOTOGRAPHING APPARATUS WITH FIRSTAND SECOND CHARGE DEVICES, Apr. 30, 1996) discusses an electrophotography apparatus with a photosensitive body, first charge devices for performing a first charge process to form an image on the photosensitive body, and two transfer chargers having the same polarity. Nimura et al.(U.S. Pat. No. 5,488,463, IMAGE FORMING APPARATUS TO FORM IMAGES ONTO A SHEET A PLURALITY OF TIMES, Jan. 30, 1996) discusses an image forming unit having first and second conveying units for conveying the sheet from the image forming unit to the image forming unit. Itani et al.(U.S. Pat. No. 5,443,873, SILICON RUBBER FOR ELECTROPHOTOGRAPHYAND METHOD OF PRODUCING THE SAME, Aug. 22, 1995) discusses an electrically conductive rubber roller for electrophotography which changes very little in electric resistance with changes in environment. Koike et al.(U.S. Pat. No. 5,426,496, PRINTING APPARATUS, Jun. 20, 1995) discusses a slim printing apparatus which employs a latent image forming method, such as electrophotographing method, and needs an apparatus-occupying area. Muramatsu et al.(U.S. Pat. No. 5,410,419, FACSIMILE MACHINE CAPABLE OF DISTINGUISHING COPIED IMAGE AND RECEIVED IMAGE, Apr. 25, 1995) discusses a facsimile machine which can set a so-called night time collective time designation mode for power saving during night time processing time. From my study of the contemporary practice and of the art, I find that there is a need for an effective and improved apparatus for optimizing an image transfer environment by detection of humidity contained in a printing medium such as paper which results in enhancement in printing quality without spots due to spreading of a developing substance such as toner.